Silver recovery

ABSTRACT

Equipment and methods for recovering silver from a silvercontaining solution. The equipment comprises a plastic container and rotatable spaced T-connectors comprising an influent liquid passage and an effluent liquid passage. A transparent U-shaped tube with an elevated aperture therein spans between the two Tconnectors. The influent and effluent liquid passes through fittings in a lid which fittings are externally sealed adjacent respective openings in the lid. The circumference of the lid comprises a female slot ending in a downwardly extending exposed lip or flange. The lid and container are thus joined in releasable press-fit relation during use. The fittings, carried at the mentioned apertures in the lid, are each in two parts, one threaded into the other from opposite sides of the lid. A recovery element made of a metal above silver in the electromotive force series fits within the container. The metalforming the element is arranged in a woven matrix, such as, for example, galvanized window screen, which is wound upon itself around its longitudinal axis which is offset from but parallel to the axis of the container to form a hollow cylinder having an inside surface and an outside surface and which is transversely pervious in respect to the container. A pedestal of wood with a male extension disposed in the hollow of the coil supports the coil well above the bottom of the container, where sludge collects. The influent passages are in liquid communication with the interior of the container adjacent the outside surface and near the bottom of the element, and the effluent passage is in liquid communication with the hollow interior and near the top of the element. The influent passage terminates within the container in a baffle comprising a T-shaped fitting. The solution precipitates silver in exchange for the metal of the woven matrix.

United States Patent [191 MacKay 1 SILVER RECOVERY [76] Inventor:Michael T. MacKay, 2160 I Streamview, Sandy, Utah 84070 [22] Filed: Nov.2, 1973 [21] Appl. No.: 412,090

[52] US. Cl. 266/22, 7 5/l09 [51] Int. Cl C22b 11/12 [58] Field ofSearch 266/12, 22; 75/108, 109, 75/118 [56] References Cited UNITEDSTATES PATENTS 3,692,291 8/l970 MacKay 266/22 Primary ExaminerGerald A.Dost Attorney, Agent, or Firm-Lynn G. Foster ABSTRACT Equipment andmethods for recovering silver from a silver-containing solution. Theequipment comprises a plastic container and rotatable spacedT-connectors comprising an influent liquid passage and an effluentliquid passage. A transparent U-shaped tube with an elevated aperturetherein spans between the two T- connectors. The influent and effluentliquid passes through fittings in a lid which fittings are externallysealed adjacent respective openings in the lid. The circumference of thelid comprises a female slot ending in a downwardly extending exposed lipor flange. The lid and container are thus joined in releasable press-fitrelation during use. The fittings, carried at the mentioned apertures inthe lid, are each in two parts, one threaded into the other fromopposite sides of the lid. A recovery element made of a metal abovesilver in the electromotive force series fits within the container. Themetal-forming the element is arranged in a woven matrix, such as, forexample, galvanized window screen, which is wound upon itself around itslongitudinal axis which is offset from but parallel to the axis of thecontainer to form a hollow cylinder having an inside surface and anoutside surface and which is transversely pervious in respect to thecontainer. A pedestal of wood with a male extension disposed in thehollow of the coil supports the coil well above the bottom of thecontainer, where sludge collects. The influent passages are in liquidcommunication with the interior of the container adjacent the outsidesurface and near the bottom of the element, and the effluent passage isin liquid communication with the hollow interior and near the top of theelement. The influent passage terminates within the container in abaffle comprising a T-shaped fitting. The solution precipitates silverin exchange for the metal of the woven matrix.

7 Claims, 3 Drawing Figures PATENTED GET 8 4 II I -FlG.2

FIG. 3

SILVER RECOVERY BACKGROUND 1. Field of Invention This invention relatesgenerally to silver recovery and more particularly to a silver recoveryunit having an improved structure comprising a plastic container andpress-fit lid using rotatable influent T fittings, threaded lidfittings, an eccentric metal fabric coil, a coil pedestal support and abaffled influent opening and effluent openings of substantiallydifferent elevations within the container.

2. Prior Art Various silver salts used in photographic paper and filmwhen fixed by various fixatives produce a complex silver salt which isdissolved or suspended in solution. As the fixatives become depleted,replacement is nec: essary to keep the fixing solution at a satisfactorystrength if uniform and acceptable results are to be obtained. Thisreplenishment is often accomplished on a continuing basis by theaddition of a given volume of concentrated solution of fixatives to thefixing bath, while at the same time an equivalent volume of spentsolution is withdrawn.

A technique forrecovering silver from such spent solutions has beendeveloped. The technique requires the passing of solutions containingsilver salts through packed steel wool or small cut pieces of galvanizedwindow screen. The steel wool and pieces of screen are anodic to silverso that a chemical replacement action will occur, which causesprecipitation and deposition of the silver as the steel wool or piecesof screen dissolve. The disadvantage of packed steel wool has been itslack of resistance to corrosion caused by the fixing solution.Specifically, the steel wool fibers are small in diameter and,therefore, readily dissolved by the solution. The result is thatrelatively large openings develop in the steel wool and the fixingsolution, thereafter, flows through the openings rather than through theremaining packed steel wool fibers since the openings present lessresistance to flow. The steel wool must be replaced once the existenceof such openings is discovered in order to restore satisfactoryefficiency to the silver recovery unit.

Also, silver recovery units of the prior art have been expensive tomanufacture, use and maintain. Frequent clogging has occurred andinefficient recovery of silver experienced. Also, flow patterns throughprior art silver recovery units have resulted in inefficient recovery ofsilver because of poor contact with the exchange metal and lackversatility in the placement of such unit has been restrictive.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION The mentioned disadvantagesof prior art silver recovery units have been substantially alleviated orovercome by the present invention,-which comprises a plastic containercovered by a press-fit plastic lid. Rotatabl'e T-connectors above thelid can be selectively set to direct influent and effluent liquid to andfrom the container in a plurality of directions. A U-shaped transparentoverflow tube joins the two T-connectors. The lid presents spacedapertures with water tight interrelated fittings on each side of the lidat each aperture through which influent and effluent solution passes.So-

lution flow within the container passes a transversely pervious metalliccore eccentrically disposed within the container upon a retainingpedestal well above the bottom of the container. The core is constructedfrom axially oriented, coiled screen with small mesh openings. Theinfluent passage terminates within the container near the bottom at abaffle adjacent the outside of the coil, while the effluent passagecommences within the container near the top at the hollow interior ofthe coil.

The result is that silver recovery units according to the presentinvention and inexpensive and easy to use, circulation is improved andefficiency is high until the replaceable metallic core has been fullyutilized and the operation of the unit is not normally subject tointerruptions due to pre-mature clogging. The units may be placedanywhere and solution flow adjusted to suit the physical conditions ofplacement.

An emergency overflow transparent conduit with a gravity port connectsthe influent and effluent passageways above the lid to accommodateprompt discharging of influent solution when a surge of solution orunexpected clogging of the container occurs.

It is a primary object of this invention to provide an improved silverrecovery apparatus and method.

Another important object of the present invention is to provide animproved silver recovery apparatus and method wherein novel flowmechanisms wherein clogging is alleviated and silver recovery maximized.

It is a further significant object of this invention to provide a silverrecovery unit having selectively settable improved solution flow paths.

It is another paramount object of this invention to insure bottom to topsolution flow within a silver recovery container with intermediate flowbeing transverse through a laterally pervious coil of metal.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view with partsbroken away for clarity of illustration of a presently preferredembodiment of this invention;

FIG- 2 is a longitudinal cross sectional view taken along line 2-2 ofFIG. 1; and

FIG. 3'is a fragmentary perspective of the lid of FIG. 1 showing the twoT-connectors and the U-shaped overflow tube removed from oneT-connector.

DETAILED DESCRIPTIONOF THE ILLUSTRATED EMBODIMENT As shown in FIGS; 1, 2and 3, a silver recovery unit, generally designated 2, comprises abucket or container 4, of polyethylene or other suitable chemicallyinertplastic, a lid or closure 6, liquid effluent and influent connectorstructures 8 and 10, and a metallic core 12, which is located ingenerally axial relation, within the container 4 and is in liquidcommunication with the influent connector structure 10 and the effluentconnectorstructure 8.

The silver recovery unit 2, as mentioned, comprises container 4, whichterminates in an elevated opening at 14 away from which projects aradial lip 16, together with the dish-shaped closure or lid 6. Thecontainer 4 and lid 6 are respectively fabricated of material which isinert to the photographic solutions to be treated and are press-fittogether so that the lid 6 closes the opening 14 such that the removablelip 16 fits snugly within a matching female groove 18 disposed betweentwo essentially coextensive, though spaced flanges 20 and 22, whichcomprise part of the lid or closure 6 and extend downwardly. A ribbon ofsealant composition (not shown) may be extruded between the flanges 20and 22 at groove 18 so that a totally impervious fluid seal isestablished between the container 4 and the lid 6. A suitable sealantcomposition comprises RTV silicone rubber sealant, manufactured by theGeneral Electric Co., Silicone Products Department, Waterford, New York.Other acceptable sealants are also available.

The closure or lid 6 defines a plate 24 through which two apertures 26and 28 extend. Each aperture 26 and 28 receives a fitting 30 comprisinga hollow housing 32, with a threaded reduced diameter male extension 33,and a hollow interiorly threaded shaft 34. When snugly threaded togethereach fitting 30 creates a fluid tight relationship with the lid 6. Ashort plastic tube 36 passes into each housing 32 in press-fit andpreferably bonded relation and concentric with the axis (not shown) ofthe housing 32 and the threaded shaft 34. A further short plastic tube56 depends from the interior of the more centrally located one of thetwo fittings 34 in press-fit and preferably bonded relation. Tube 56 isnear the top of the container 4 within the hollow of the core 12 andcomprises the beginning component of the effluent connector structures8.

The influent connector structure 10 comprises a relatively longdischarge plastic tube 58, which is press-fit in sealed and preferablybonded relation with the lower opening of the most eccentric one of thefittings 34. Thedischarge tube 58 terminates in a T-connector baffle 60,press fit and preferably bonded to the lower end of the tube 58, suchthat solution is discharged horizontally through opposite dischargeopening 61 of the baffle 60. If desired short tubes (not shown) may bepress fit into each opening 61 to further distribute influent solutionwithin the container 4 about the coil 12. In each unbonded press-fitunion, a firm, liquid-tight seal may be created by extruding a ribbon ofsuitable nonsetting sealant into the union. When desired, the unit maybe readily disassembled by physically separating each unbonded press-fitand each threaded union. By the same token, the lid 6 together with theinfluent and effluent connector structures 10 and 8 can be unitarilyremoved from the container 4 by manually releasing the press-fitconnection at bead 16. With the lid or closure 6 removed, the metalliccore 12, hereinafter more fully described, can be insertedor removed,and the silver sludge deposited by reason of the chemical action betweenthe core 12 and the solution being processed can also be removed.

A T-connector 48 is joined at the top of each short tube 36 inpress-fit. unbonded relation. Each T- connector 48 has two openingslocated vertically one above the other, the lower of the two receivingone short tube 36 as mentioned. A third, horizontal opening isadjustable by rotation of the T-connector about the short tube 36. Thus,the direction of arrival at the influent T-connector 48 may be adjustedto suit the physical circumstances in which the unit 2 is placed in agiven installation and the effluent issuing from the effluentT-connector 48 may likewise be directed so as to best suit thecircumstances of use of the unit 2. The influent T-connector 48 receivesinfluent solution tube 46 in press-fit relation at the horizontalopening of the T- connector, which may be bonded or unbonded, dependingupon preference. Likewise, effluent tube 68 is press-fit into thehorizontal opening of effluent T- connector 48 to accommodate discharge.

A flexible U-shaped tube 74 spans between the upper vertically orientedopening of each of the two T- connectors 48 and comprises an overflowpath. The tube 74 is transparent to facilitate visual observation ofoverflow so that the user of the unit 2 may readily ascertain excessiveinfluent solution flow or clogging as the case may be. Gravity pressureis maintained by reason of an elevated aperture 76 at the highest pointin the inverted U tube 74.

It is to be appreciated that for gravity flow operation, effluent tube68 should be slightly lower in elevation than influent tube 46. Use of acoating comprised of stop cock grease between the contiguous surfaces ofassociated ones of T-connector 48 and short tube 36 and the connectionsurfaces between connectors 48 and tube 74 will accommodate relativerotation and removal of the mentioned components without creatingleakage problems. One of several suitable stop cock greases isidentified as Silicone Lubricant manufactured by Dow Coming of Midland,Michigan.

It should be readily apparent that the material or materials from whichthe components of the influent connector structure 10 and the effluentconnector structure 8 are made must inherently comprise plastics whichare inert to the silver-containing fixing solution processed through thesilver recovery unit 2.

If desired, end 78 of tube 74 can be removed from the upper verticallyoriented opening of T fitting 48 thus providing an examination sitewhere the solution being discharged can be inspected or tested.

The metallic core 12 is transversely permeable and comprised of metalwhich is above silver in the electromotive force series. Althoughseveral such metals are known which will perform. satisfactorily, it hasbeen found that iron in the form of woven pervious screen is well suitedto this use.

The coiled screen 12 is preferably retained in the illustratedconfiguration by use of several belt-type or wire like fasteners 84 eachof which forms a loop about the coiled screen to retain the generallycylindrical tightly wound configuration. It is convenient to place orreplace the coil of metal screen within the container 4 by merelyremoving the closure 6 from the container 4 and situating the tightlycoiled screen in the position illustrated in FIGS. 1 and 2.Consequently, the core 12 defines a longitudinally-extendingeccentrically disposed cylinder defining anoutside surface 86 and aninside surface 88.

The bottom 90 of the coil 12 rests on interlocking crossed beams 92 and94 of a wooden pedestal 95, which beams are slotted so as to fittogether in male/- female relation. The coil 12 is held eccentricallystationary with respect to the crossed beams by such means as metalspikes (not shown) extending from the top of the beams 92 and 94 intothe coil between the layers thereof.

A male plug 96 is attached to a top pedestal plate 98, and is made fromsome suitably non-reactive material. The plug is sized and shaped to fitsnugly within the lower end of the hollow interior 88 of coil 12 andprevent upward axial flow of solution from space A to interior 88 andalso maintain the coil in the illustrated eccentric position. End plate98 may be made of a flexible material such as rubber sheeting to insurean absence of upward flow from space *A" to interior hollow 88.

The top of the core 12 supports a horizontally oriented thin imperviouscover 100 tightly secured to coil 12 by means such as metal spikes (notshown) extending through the cover 100 into the core between the coilsthereof. The cover 100 has a central opening 102 which loosely receivesthe effluent filling 34, thereby forcing the transverse solution flowmentioned earlier. A hole 104 off of center in cover 100 looselyreceives tube 58.

Silver-containing sludge once removed from the container 4, is reducedto elemental silver by conventional processes.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

l. A fluid tight silver recovery unit accommodating fluid flowtherethrough under force of gravity: a container comprising a bucketcomprised of plastic material inert to photographic fixing solution, thebucket being closed at one end and along the length thereof and having alarge opening at the other end thereof and a lid sized and shaped toclose the opening of the container and comprised of plastic materialinert to photographic fixing solution, said bucket and lid togetherpresenting opposed mating male-female press-fit sealing adjacent theopening of the bucket for releasably fastening the bucket and the lidtogether, the lateral dimensions of each being essentially the same, thelid receiving liquid-conducting influent and effluent means comprised ofplastic material inert to photographic fixing solution for introducingand removing solution from the container and influent means comprising aT- connector rotatably coupled to adjacent components of said influentmeans for selectively setting the direction of influent flow ofsolution, said effluent means comprising a second T-connector rotatablycoupled to adjacent components .of said effluent means for selectivelysetting the direction of effluent flow of solution, the influent meansand effluent means each further comprising male and female fittingscoupled together in sealed relation against the top and bottom surfacesrespectively of the lid, and a hollow coil of transversely perviousexchange metal disposed within the container and said influent meanscomprising a baffled distal end terminating within the container nearthe bottom thereof adjacent the'exterior of the coil of metal and saideffluent means beginning within the container near the top thereofwithin the hollow of the coil.

baffled distal end comprises a T-fitting with one vertically orientedpassage coupled to an adjacent component of the influent means and twohorizontally oriented passages opening communicating solution into thecontainer.

3. The silver recovery unit of claim 1 further comprising:

a flexible transparent inert plastic tube spanning between topvertically oriented passages of said two T-connectors to accommodatesolution overflow.

4. The silver recovery unit of claim 3 wherein:

said transparent inert plastic tube is removable from the effluentT-connector to allow for inspection and testing of effluent solution.

5. A fluid tight silver recovery unit accommodating fluid flowtherethrough under force of gravity comprising: a container comprising abucket comprised of plastic material inert to photographic fixingsolution and having an opening at one endthereof and a lid sized andshaped to be compatible with the container and comprised of plasticmaterial inert to photographic fixing solution, the bucket and lid beingdisposed in releasably sealed relation adjacent the bucket opening, thelid comprising two spaced apertures respectively receiving fitting meansof material inert to photographic fixing solution respectively in sealedrelation with the lid at the associated aperture and each fitting meansdefining interior passage means for introducing and removing solutionfrom the container utilizing influent means and effluent meansrespectively comprising said fitting means, a centrally hollow metalliccore disposed within the container having a cylindrical configurationand an axis essentially parallel to but eccentric to the axis of thecontainer, the metallic core comprising a metal higher than silverin theelectromotive force series and being substantially impervious to fluidflow in the axial direction but defining a plurality of liquid flowpaths essentially transverse of the axis of the metallic core, andwherein the influent means terminates at a baffled end thereofimmediately adjacent the outside cylindrical surface of the metalliccore near the bottom of the bucket and the influent means commenceswithin a central hollow of the core near the top of the bucket. 1

6. The silver recovery unit of claim 5 further comprising:

a pedestal of substantial height interposed between the bottom of thebucket and the core, the core resting thereon, the pedestal being of amaterial inert to photographic fixing solution.

7. The silver recovery unit of claim 6 wherein:

said pedestal further comprises an upwardly extending male projection,sized and shaped to be compatible with the hollow of the core, extendinginto said hollow to retain said core in said elevated eccentricdisposition within the bucket in parallel relation with the longitudinalaxis of the bucket. k

1. A fluid tight silver recovery unit accommodating fluid flow therethrough under force of gravity: a container comprising a bucket comprised of plastic material inert to photographic fixing solution, the bucket being closed at one end and along the length thereof and having a large opening at the other end thereof and a lid sized and shaped to close the opening of the container and comprised of plastic material inert to photographic fixing solution, said bucket and lid together presenting opposed mating male-female press-fit sealing adjacent the opening of the bucket for releasably fastening the bucket and the lid together, the lateral dimensions of each being essentially the same, the lid receiving liquid-conducting influent and effluent means comprised of plastic material inert to photographic fixing solution for introducing and removing solution from the container and influent means comprising a T-connector rotatably coupled to adjacent components of said influent means for selectively setting the direction of influent flow of solution, said effluent means comprising a second T-connector rotatably coupled to adjacent components of said effluent means for selectively setting the direction of effluent flow of solution, the influent means and effluent means each further comprising male and female fittings coupled together in sealed relation against the top and bottom surfaces respectively of the lid, and a hollow coil of transversely pervious exchange metal disposed within the container and said influent means comprising a baffled distal end terminating within the container near the bottom thereof adjacent the exterior of the coil of metal and said effluent means beginning within the container near the top thereof within the hollow of the coil.
 2. The silver recovery unit of claim 1 wherein said baffled distal end comprises a T-fitting with one vertically oriented passage coupled to an adjacent component of the influent means and two horizontally oriented passages opening communicating solution into the container.
 3. The silver recovery unit of claim 1 further comprising: a flexible transparent inert plastic tube spanning between top vertically oriented passages of said two T-connectors to accommodate solution overflow.
 4. The silver recovery unit of claim 3 wherein: said transparent inert plastic tube is removable from the effluent T-connector to allow for inspection and testing of effluent solution.
 5. A fluid tight silver recovery unit accommodating fluid flow therethrough under force of gravity comprising: a container comprising a bucket comprised of plastic material inert to photographic fixing solution and having an opening at one end thereof and a lid sized and shaped to be compatible with the container and comprised of plastic material inert to photographic fixing solution, the bucket and lid being disposed in releasably Sealed relation adjacent the bucket opening, the lid comprising two spaced apertures respectively receiving fitting means of material inert to photographic fixing solution respectively in sealed relation with the lid at the associated aperture and each fitting means defining interior passage means for introducing and removing solution from the container utilizing influent means and effluent means respectively comprising said fitting means, a centrally hollow metallic core disposed within the container having a cylindrical configuration and an axis essentially parallel to but eccentric to the axis of the container, the metallic core comprising a metal higher than silver in the electromotive force series and being substantially impervious to fluid flow in the axial direction but defining a plurality of liquid flow paths essentially transverse of the axis of the metallic core, and wherein the influent means terminates at a baffled end thereof immediately adjacent the outside cylindrical surface of the metallic core near the bottom of the bucket and the influent means commences within a central hollow of the core near the top of the bucket.
 6. The silver recovery unit of claim 5 further comprising: a pedestal of substantial height interposed between the bottom of the bucket and the core, the core resting thereon, the pedestal being of a material inert to photographic fixing solution.
 7. The silver recovery unit of claim 6 wherein: said pedestal further comprises an upwardly extending male projection, sized and shaped to be compatible with the hollow of the core, extending into said hollow to retain said core in said elevated eccentric disposition within the bucket in parallel relation with the longitudinal axis of the bucket. 